abstract class Fruit {
    public abstract void eat();
}

// ================== 叶子节点 ==================
class Apple extends Fruit {
    @Override
    public void eat() {
        System.out.println("吃苹果");
    }
}

class Banana extends Fruit {
    @Override
    public void eat() {
        System.out.println("吃香蕉");
    }
}
